We are all aware that propane is a safe and convenient fuel for heating homes, drying clothes, and cooking steaks on the grill, but did you know that propane can also be used to safely add power, torque, and range to your Cummins-powered Dodge truck? That's right, diesel engines actually respond very well to propane injection as a power adder and the Cummins is no exception. The Cummins engine is powerful in stock form, but who can leave anything stock?

With so much aftermarket power-adding equipment available, we just couldn't leave well enough alone. It started with wanting to add just enough power to our '01 dualie so the transmission wouldn't downshift when towing our car trailer up inclines, but like most gearheads once we started exploring how much power these engines can make, we couldn't stop. After adding an Edge computer, wastegate controller, and free-flowing exhaust, and burning up our torque converter, requiring it to be replaced with a beefier unit, we still wanted more. Our research led us to MSD ignition's web site where we learned about their Digital Propane Injection.

Propane has been used as an automotive fuel for quite some time in gasoline engines and though slightly less efficient than gasoline is an extremely clean burning fuel. A diesel engine operates somewhat differently than a gasoline engine taking in the maximum amount of air possible during each intake stroke. Engine speed is then determined by varying the amount of diesel fuel injected into the cylinders. The result is that there is nearly always extra oxygen in the cylinders that has not been used up in the combustion process. When propane is injected into the cylinders through the intake system it bonds with the additional oxygen and combusts with the rest of the fuel resulting in substantial gains in power and torque. The same power can be attained by adding more diesel fuel, which is the premise used by computer programmers or "chips," but the extra amount of diesel necessary to make the same power as propane is usually not feasible without making costly fuel system modifications. Diesel fuel also burns at a slightly higher temperature than propane, so exhaust temperature can limit the amount of power that can be attained through increasing the amount of diesel fuel injected into the engine. An additional benefit of using propane to increase power is that propane is a clean burning fuel, not adding the soot or emissions that diesel fuel does. Considering our power adding options, we decided to try MSD's new system and find out for ourselves how it worked.

The only real concern with propane injection is metering the propane properly so that engine damage does not occur. Just hooking up a hose from the bottle on your gas grill and feeding propane into the engine may give you a heck of a kick in the pants one time, but the engine will certainly over rev or overheat causing damage. The amount of propane needs to be controlled depending on engine parameters, such as boost, throttle position, and rpm. MSD's system not only monitors the engine parameters necessary to ensure proper metering of the extra fuel, but is completely tunable using a laptop computer and the included software depending on the level of performance you wish to achieve. The system also has several built-in safety features that ensure engine damage does not occur. A common misnomer is propane is like "nitrous oxide for a diesel," which is completely untrue. Nitrous oxide instantly boosts cylinder pressures and temperatures shocking the motor's pistons and rods when used. Contrarily, propane is injected gradually as the engine needs it and burns smoothly with the rest of the combustion mixture without the "shock" effect on the pistons and rods that nitrous oxide has. The MSD system is actually controlled through a closed loop ECM that is separate from your truck's computer system, constantly monitoring engine parameters as well as propane pressure and temperature to ensure safe operation. If any parameter is out of range, the system will shut down and propane will not be injected into the engine.

When ordering our kit, we were informed by MSD that while we could install most of the items ourselves, the propane tank must be purchased separately and meet both federal DOT and state and local requirements. they recommended that Southeast Power Systems in Orlando install our tank. The Digital Propane Injection system consists of three main parts: the Electronic Control Unit (ECU), the regulator assembly, and the tank. Even having to assemble the regulator assembly, reroute a heater hose to the regulator, and extend several of the wires in the provided wiring harness, we found it easy to install the components in a little over six hours. Other than drilling mounting holes for the ECU and regulator, nothing more than basic hand tools were needed to accomplish the job. We found the kit to be complete, and the instructions were thorough and concise. Having the tank installed at Southeast Power Systems took the better part of a day; we chose the more complex under-bed installation with a remote fill station at the rear bumper. In-bed installations are less complex and take less time. A concern was how our truck would act when propane injection was added to the modifications we had already performed to our truck. The folks at MSD assured us that propane injection complements other power-adding modifications and is completely "stackable" with computer controllers and intake and exhaust modifications. Power and torque will show the most gain on a stock vehicle and slightly less on a modified vehicle. The end result of adding propane to a modified vehicle will still be greater than the vehicle had before, but will never add up to the sum of the advertised gain of each component.

After our kit was installed, we were thoroughly impressed with both the performance gain as well as the increased economy shown in our truck. The system worked flawlessly from the first time we used it and added substantial power to our already healthy Dodge. We tested the system with the truck both loaded and unloaded and were impressed with the improvement in acceleration. We initially programmed the system to give us 100-percent capacity at 5 pounds of boost and expected to feel the system's "hit" when the propane was added. The system operated seamlessly, however, and the only indication that it was working was the speedometer's rapid acceleration to not-quite-legal speeds. Even when only programmed to 50-percent capacity while towing our 10,000-pound, enclosed car trailer, we found we had power to spare. No matter what incline we climbed, simply rolling into the throttle produced not just sustained speed, but acceleration, with transmission downshifts now a thing of the past. Exhaust temperature was also noted to be some 50 degrees cooler for a given driving parameter. A quick trip down the eighth-mile showed an improvement of six-tenths of a second and 5 mph when using the propane, with traction now limiting how hard we could launch the truck. Amazingly, it also makes economical sense to use the system when driving daily.

As a function of the extra power on tap, the economy of our truck improved drastically. In a controlled test at 65 mph, our highway mileage in an unloaded truck with the propane shut off was 24 mpg, not bad for a heavy dualie. With the propane injection on and set to initiate at five pounds of boost and give 50 percent of the systems capacity, our mileage increased to an amazing 44 mpg (factoring the diesel fuel used only)! Over a 100-mile test, we used 6 pounds of propane from our 30-pound tank, which cost $18 to fill at the local propane supplier, so the propane used for the test cost $3.60. Diesel fuel for the 100 miles was 2.27 gallons at $3 per gallon for a total of $6.82 in diesel fuel. Added together we get a total of $10.42 for the 100-mile test using propane. Without propane, we used 4.17 gallons of diesel at $3 per gallon for a total of $12.50, so we saved over $2 on a 100-mile test using propane. In addition to the cost savings, the use of propane provided us added range, which allowed us to shop for fuel, saving additional money because we now could go to the next exit or even the next state to find cheaper fuel. Even better results were obtained when towing-we saw mileage increase from 14 mpg without propane to 24 mpg when using propane injection. Our truck's range now had no problem exceeding the endurance of our bladder, even while towing our car trailer. We can derive mathematically that it doesn't take too long for the system to pay for itself, especially when diesel fuel in our area is hovering around the $3-per-gallon mark.

What can we say? Easy installation, clean, safe power, improved economy, and a system that pays for itself adds up to one of the best improvements you could make to your diesel-powered truck.